The present invention relates to a photoelectric switch in which a light-emitting section composed of a plurality of light-emitting elements is confronted with a light-detecting section composed of a plurality of light-detecting elements, thus forming a multi-optical-path. More particularly, the invention relates to a photoelectric switch in which the degree of freedom in the arrangement of optical paths is improved.
Heretofore, in order to detect the presence or absence of an object in a predetermined plane, a photoelectric switch as shown in FIG. 35 has generally been employed. The switch has a light-detecting section 1 in which a plurality of light-detecting elements 2 are arranged in a line, and a light-emitting section 3 in which a plurality of light-emitting elements 4 are arranged in such a manner as to confront with respective ones of the light-detecting elements 2. Accordingly, a plurality of optical paths 5 are formed between the light-detecting elements 2 and the light-emitting elements 4.
When an object to be detected enters a detection plane 6 (indicated by a two-dot chain line) and crosses at least one optical path 5, a light beam from at least one light-emitting element 4 is not applied to the confronting light-detecting element 2, whereby the presence of the object can be detected.
However, the above-described photoelectric switch suffers from the following difficulties:
The light-emitting section 3 and the light-detecting 1 section are constant in length. Hence, in order to change the size of the detection plane 6 according to the object to be detected, a plurality of photoelectric switches different in length must be provided.
Depending of the configuration of the object to be detected (hereinafter referred to merely as "an object" when applicable), for instance in the case of an object having a hole, sometimes it is necessary to provide a non-detection region in a part of the detection plane 6. In this case, it is necessary to additionally provide a photoelectric switch which has a non-detection part. Furthermore, in order to change the position of the non-detection region, it is necessary to provide a photoelectric switch which is different in the arrangement of light-emitting and light-detecting elements.